1. Field of the Invention
The present invention relates to a container opening/closing device for opening and closing a lid of a container.
2. Description of the Related Art
A wafer transporting container such as an FOUP (Front-Opening Unified Pod) or FOSB (Front Open Shipping Box) includes an opening/closing mechanism provided in a load port, and wafers are loaded into or unloaded from the container by opening and closing a door forming the lid of the container by using this opening/closing mechanism. To prevent the removal of the door and the falling of wafers inside the container from it during the transportation of the container, it is necessary to reliably close the door at the load port. Therefore, a device for checking whether the door is properly closed has been proposed (Japanese Patent Laid-Open Nos. 2008-100635, 2009-200200 and 2009-239004).
For the FOUP and FOSB, the upper limit of a force required to close the door is defined by the SEMI standards. Manufacturers of the FOUP and FOSB design them so that the door can be closed by a force not exceeding the upper limit defined by the SEMI standards. Based on the upper limit defined by the SEMI standards, therefore, a load port manufacturer designs the opening/closing mechanism so that the door can reliably be closed.
Since the sizes of wafers more and more increase, it has become necessary to close the door of a container such as the FOUP or FOSB containing wafers by using a larger force in order to fix and hold large-sized wafers. Consequently, the upper limit defined by the SEMI standards also change in accordance with the size of a wafer.
When the wafer size is 300 mm that has been the most popular size, the upper limits of the SEMI standards produce no large difference between the FOUP and FOSB. Accordingly, the load port opening/closing device is often designed based on the upper limit of the FOSB, and made usable for both the FOSB and FOUP.
When the wafer size is 450 mm, however, the upper limits of the SEMI standards have a large difference between the FOUP and FOSB. When the load port opening/closing device is designed based on the upper limit of the FOSB, the device is over-engineered for the FOUP, and the cost increases because the driving force is large. The ratio of FOUPs is generally higher than that of FOSBs as containers manufactured in a single factory. Therefore, the installation cost increases if the FOSB load port is used as the FOUP load port. By contrast, when the load port opening/closing device is designed based on the upper limit of the FOUP and used for the opening/closing of the FOSB, a door closing error may occur due to the insufficiency of the driving force.